boston built the first modern sewer system in the united states. ours was completed between 1877 and 1884. with this wonderful new sewer system, we were taking our filth and moving it out to the ocean. of course, all of this was untreated. in the 1960s, we were still pumping all of our sewage out to moon island, untreated. we would get swimmers here, never knowing, in the middle of summer, why you would have a cold. well, we were swimming in diluted sewage. melosi: the major way to deal with pollution, at least until early into the 20th century, was through the process of dilution. the assumption was that the capacity of rivers and streams, and even the seas, allowed for certain levels of pollution that eventually would purify themself.